Canterbury has been rattled by more than 30 aftershocks over the past 12 hours.
As the city mops up after yesterday afternoon's severe 5.7 magnitude jolt a flurry of smaller shallow quakes continued to keep the city on edge.
Most of the aftershocks were 10km deep and located between 5km and 10km northeast of Christchurch.
The strongest quake was a 4.2 magnitude quake that was felt at 6.27pm.
Canterbury District Health Board spokeswoman Amy Milne said fewer than 10 people presented at Christchurch Hospital's accident and emergency department with minor injuries following the quake.
She did not have details of their injuries, but none were admitted.
There were also no heart-related presentations or admissions as a result of yesterday's shake, she said.
This morning, Christchurch Mayor Lianne Dalziel will meet with GNS Science experts.
Ms Dalziel told the Herald just before 7am there had been no new reports of damage, road closures or other quake-related problems overnight.
She would now hear from seismologists about the latest aftershock in a sequence of more than 15,000 since the city was first rattled by the 7.1 Darfield earthquake in September 2010, and almost five years to the day since the 6.3 magnitude jolt that killed 185.
"I'm getting a briefing from GNS this morning. They are saying this is not unexpected in terms of the sequence of events ... there have been more than 50 aftershocks over 5 [magnitude] since September 2010. I just think it's been a bit of a shock to people because there hasn't been one for a while.
"My message is just be aware that people who are feeling vulnerable need a bit of support. Just look after each other. I think that Christchurch has shown we are very good at doing that."
KiwiRail spokeswoman Joanne Black this morning said there was no quake-related disruption for the railways today.
"Lines were closed yesterday while tracks and structures, mostly bridges and tunnels, were checked. No problems were found and all lines were re-opened as they were cleared."
Christchurch Airport spokeswoman Yvonne Densom said the airport was open this morning, as it had been during and following yesterday's shake.
Jetstar spokesman Phil Boeyen said flights in and out of Christchurch were running on schedule this morning.
Air New Zealand couldn't be contacted this morning, but the airport's website showed flights were arriving and departing as normal.
Transport for Christchurch spokeswoman Tresca Forrester said the main disruption remained in the east of the city.
Bower Ave in North New Brighton was open, but traffic was slowed by a liquefaction-caused sinkhole in the middle of the road near Crofts Lane.
Scarborough Rd, open only to residents after yesterday's quake, had reopened to the public, Ms Forrester said.
Other roads in Shirley and Merivale were yesterday affected by burst water mains, and motorists should be aware of this if travelling in the area.
Whitewash Head Rd, in Scarborough, was open, but access to the walking track at the top of the road was closed.
The New Zealand Transport Agency checked all state highways, including the Lyttelton Tunnel, yesterday and all were cleared to remain open.
The agency had told Ms Forrester extra checks would take place this morning on the tunnel and Anzac Bridge, which was badly damaged in the February 2011 aftershock.
To add to Christchurch's woes, a thick blanket of fog covered the city's Northern Motorway this morning. That led to a slow journey into the city for commuters, but the fog had cleared by 9am, she said.
Seismologist Ana Kaiser said yesterday's quake - just a week out from the five-year anniversary of the devastating 2011 quake - now raised the probability of more strong mid-range magnitude earthquake activity in the future.
"The likelihood of earthquakes between magnitude 5 and 5.9 and 6 and 6.9 has increased somewhat following the quake yesterday," she said.
But the probability of the region being struck by an earthquake above magnitude 7 or greater still remained under 1 per cent.
She said there was no way to predict earthquake activity but there was nothing untoward in the 2010 Canterbury quake sequence leading up to yesterday's tremor.
"It is certainly part of the same earthquake sequence and that sequence is still ongoing."
She said depending on the tectonic setting the quake sequence could last for up to a decade.
Where the earth's plates were compressing or expanding at a smaller rate there was typically a longer earthquake sequence, she said.
The Canterbury quakes were behaving similar to this type of movement.
She said seismologists would be monitoring the number of aftershocks and for patterns, including locating precisely where they were happening and the space between each jolt.
They would also be closely looking at the seismogram and examining the first quake which struck at 1.13pm yesterday to determine exactly how it happened and precisely what kind of fault action occurred.
Canterbury police reported a quiet night with no earthquake related calls.
Seniors golf tournament still on despite quake damage
A seniors golf tournament in Christchurch has gone ahead today despite parts of the course being damaged by the Valentine's Day quake.
When the magnitude 5.7 jolt struck yesterday afternoon, organisers of the Waimairi Golf Club's second annual senior pro-am tournament immediately feared the worst.
With 45 professionals and 38 amateur teams entered to play today, they hoped they'd escaped the liquefaction which severely damaged the course in the February 2011 quake.
But after an inspection of the lush fairways and greens, officials found liquefaction was isolated to a few places on the back nine holes.
The 15th hole was the worst affected, club-captain Fred Poskitt said, but thankfully the newly-redesigned and "quake-proofed" course had coped well and the popular tournament could go ahead.
Only one player in the field had to pull out - a building inspector.
"We're lucky that despite the good shake we came out pretty well and can play today - especially good news for our charity," Mr Poskitt said.
All funds raised goes to city sports youth charity, Active Community Charity Trust.
A meet-the-pro night at major sponsors, Winnie Bagoes went ahead as planned last night and raised more than $8000.
- additional reporting Kurt Bayer